Treatment of fabrics



Jan. 18, 1955 J. A. NEWNAM TREATMENT OF FABRICS Filed Aug. 30, 1950 I N V EN TOR.

JAMES A NEWMAfl l BY Wm JTMMM A T TORNEY United States Patent @fiice 2,699,592 Patented Jan. 18, 1955 TREATMENT OF FABRICS James A. Newnam, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application August 30, 1950, Serial No. 182,372

6 Claims. (Cl. 2618.5)

This invention relates to a method for imparting dimensional stability to fabrics, and relates more particularly to an aqueous treatment for quickly releasing strains set up in fabrics during manufacturing operations.

As ordinarily finished, rayon fabrics are dimensionally unstable, tending to shrink or elongate in laundering as strains set up during weaving or knitting and finishing operations are released. Dimensional stability is ultimately achieved when the yarns making up the fabric achieve an equilibrium condition of crimp, but this is a slow process under ordinary conditions. Stability is not attained in the usual boil-off treatments and the fabric progressively changes its dimensions during several launderings. As a result, garments made from the unstable fabric change in size after manufacture.

It is disclosed in United States Patent No. 2,470,453 to Peter Alexander that Wool fabrics may be treated to eliminate a type of shrinkage described as felting by subjecting them to intense vibrations at the high frequencies of at least 3000, and preferably between 8000 and 500,000 cycles per second, while immersed in water. The patent teaches that the vibrations must be of such high intensity that they will coagulate a solution of egg albumen within five minutes under specified conditions, and teaches that it has not been possible to generate vibrations of suificient energy at below 3000 cycles per second. Vibrations at such frequencies are difficult to obtain, and the only types of equipment known which will do so are small in size and capable of only a small output of power. A multiplicity of these small units would be required for a commercial application and would be very costly. Hence the process disclosed does not appear to be of practical value for commercial treatment of fabrics.

It is an object of this invention to provide a method for quickly imparting dimensional stability to fabric. A further object is to provide a method for utilizing vibrational energy in the readily obtained frequencies of 200 to 1000 cycles per second to release strains set up in the fabric during its manufacture. Additional objects of the invention will become apparent from the following description and claims.

By the present invention it has been found that dimensional stability can be quickly imparted to rayon fabrics by treatment in an aqueous bath with vibrational waves in the readily obtained range of 200 to 1000 cycles per second, provided that the fabric is restrained from moving with the waves and is not restrained from dimensional changes. This may be accomplished by a process which comprises supporting dimensionally unstable fabric in an aqueous bath so that the fabric rests against a substantially rigid surface in an unstressed condition, and vibrating the bath against the fabric at a frequency of from 200 to 1000 cycles per second. The fabric can be floated against the lower side of a horizontal plate which is supported above a vibrating plate forming the bottom of a vat containing the bath. Provision can be made for moving fabric continuously through the treating bath un der substantially no tension by feeding the fabric into the bath at a rate which is properly synchronized with the rate of withdrawal. Under these conditions treatments as short as ten minutes have been found suflicient to impart dimensional stability.

The invention will be more readily understood by reference to the accompanying drawing .in which the single figure is a front elevation, partly in section, representing one form of apparatus suitable for use in practicing the process of the invention.

Dimensionally unstable fabric 1 is led from a roll of fabric 2 over a guide roll 3 and into one side of a treating vat 4. The fabric passes between a pair of driven feed rolls 6 located near the bottom of that side of the vat. The rolls are arranged to grip the fabric between them and direct it toward the other side of the vat. One or both of the rolls is driven by suitable means so that the rolls rotate at the correct speed to provide the required length of treating time for the fabric. The fabric is then passed in a generally horizontal direction to a change-ofdirection roll 7 located on the opposite side of the vat from rolls 6. The fabric changes direction around roll 7 and passes upwardly out of the vat, changes direction again around a guide roll 8, and is led to a tenter or drier or other subsequent treatment. The rate of withdrawal of the fabric from the vat is properly synchronized with the speed of feed rolls 6 so that the fabric is not under tensitfii iduring its travel through the vat from rolls 6 to re A horizontal restraining device which may be a plate, a perforated plate or a wire screen 10 is supported a short distance above the bottom of the vat so that the fabric contacts the lower surface of the plate during most of the travel of the fabric from rolls 6 to roll 7. This plate is supported by uprights ll attached to horizontal crosspiece 12, which is supported independently of the vat. The bottom of the vat is formed of a vibrating plate 15, which is caused to vibrate at a frequency of from 200 to 1000 cycles per second by suitable means. The means shown in the figure is a plunger 16 driven by an electromagnet 17. A modification is to use a magnetostrictive nickel rod for the plunger, with a suitable coil instead of the electromagnet 17. Alternating current of the desired frequency is supplied to the electromagnet or coil to actuate the plunger and cause the plate to vibrate.

In operation the vat is filled with aqueous bath to the level 20, so that the fabric is submerged and caused to float against the lower surface of the restraining plate. A suitable bath is water containing a small amount of soap or other detergent to help the water to wet and penetrate the fabric. The bottom of the vat is caused to vibrate to create vibrational waves in the bath of 200 to 1000 cycles per second. The dimensionally unstable fabric is passed through the vat at a rate which will provide time for the treatment to take effect, usually about 10 to 20 minutes. The fabric is restrained from appreciable vertical movement with the waves of energy by the plate 10, but is substantially free to change dimensions in a horizlontal direction and assume a dimensionally stable conition.

As an example of the effectiveness of this treatment, a swatch of rayon broadcloth 32.85 cm. long by 36.6 cm. wide was treated in a 0.10% aqueous soap solution with vibrational energy at 360 cycles per second for 10 minutes. The fabric was held about 1 inch from the vibrating bottom of the tank by a smooth steel restraining plate. After rinsing and drying, the dimensions of the swatch were 31.25 by 36.5 cm. These dimensions were not changed by subsequent laundering.

A second swatch 35.97 by 36.5 cm. was given identical treatment except that vibrational energy was not used.

3 launderings to 31.25 by 35.95 cm. after two launderings. The data is tabulated in the following table:

Treatments:

(1) Vibrated at 360 cycles/sec. for minutes while supported by restraining plate in bath. (2) Same bath as (1) but no vibrational energy. (3) No restraining plate, otherwise the same as (1).

It will be seen that laundering had no effect on the dimensions of swatch No. 1, indicating that dimensional stability was attained in the brief treatment. In each of the other cases, although the swatches were caused to shrink by the treatment bath, they continued to shrink when laundered, the decrease in area amounting to 2.7% from two launderings. From a comparison of the results with swatches 2 and 3, it is evident that vibrational energy at these low frequencies contributed nothing when the fabric was not supported against movement with the waves.

The present invention provides a quick, inexpensive and effective method for treating fabric to release strains set up during manufacture which cause a fabric to change in dimensions when laundered. In accordance with this invention a treatment of a few minutes duration imparts a dimensional stability which previously has beenobtained only after repeated launderings.

As dilferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific illustrations thereof disclosed except as defined in the appended claims.

What is claimed is:

1. A method for imparting dimensional stability to fabric which comprises subjecting a dimensionally unstable textile fabric to vibrational waves of a frequency of 200 to 1000 cycles per second in an aqueous bath while supporting the fabric in an unstressed condition against movement with said waves until the fabric has become dimensionally stable to laundering.

2. A method for imparting dimensional stability to fabric which comprises supporting a dimensionally unstable textile fabric against movement with vibrational waves in an aqueous bath against a substantially flat rigid surface facing a source of vibrational energy in the aqueous bath and supplying vibrational energy of a frequency of 200 to 1000 cycles per second from said source until the fabric has become dimensionally stable to laundering.

3. A method for imparting dimensional stability to fabric which comprises floating a dimensionally unstable textile fabric against the lower side of a substantially horizontal immovable surface submerged in an aqueous bath and supplying vibrational energy to the bath from a source below said surface at a frequency of 200 to 1000 cycles per second until the fabric has become dimensionally stable to laundering.

4. A method for imparting dimensional stability to fabric which comprises conducting a dimensionally unstable textile fabric through an aqueous bath, supporting the fabric in an unstressed condition against movement with vibrational waves of the bath during a portion of its travel through the bath, and directing vibrational energy at a frequency of 200 to 1000 cycles per second against the fabric while it is in contact with a surface, the fabric being conducted across the surface at a rate which will provide time for the fabric to become dimensionally stable to laundering.

5. A method for imparting dimensional stability to fabric which comprises conducting a dimensionally unstable textile fabric through an aqueous bath, supporting one face of the fabric against a substantially flat rigid surface which is unmoved by vibrations in said bath, con tacting the fabric with said surface in an unstressed condition, and simultaneously directing vibrational energy at a frequency of 200 to 1000 cycles per second toward the unsupported face of the fabric, the fabric being conducted across the surface at a rate which will provide time for the fabric to become dimensionally stable to laundering.

6. A method for imparting dimensional stability to fabric which comprises conducting a dimensionally unstable textile fabric through an aqueous bath, supporting the fabric in an unstressed condition against the lower side of a substantially horizontal immovable surface during a portion of its travel through the bath, and directing vibrational energy at a frequency of 200 to 1000 cycles per second upward toward said surface and the fabric supported thereon, the fabric being conducted across the surface at a rate which will provide time for the fabric to become dimensionally stable to laundering.

References Cited in the file of this patent UNITED STATES PATENTS 2,470,453 Alexander May 17, 1949 2,535,700 Seavey et al. Dec. 26, 1950 2,558,066 Wedler June 26, 1951 FOREIGN PATENTS 587,214 Great Britain Apr. 17, 1947 659,412 Germany May 3, 1938 806,030 France Sept. 14, 1936 

6. A METHOD FOR IMPARTING DIMENSIONAL STABILITY TO FABRIC WHICH COMPRISES CONDUCTING A DIMENSIONALLY UNSTABLE TEXTILE FABRIC THROUGH AN AQUEOUS BATH, SUPPORTING THE FABRIC IN AN UNSTRESSED CONDITION AGAINST THE LOWER SIDE OF A SUBSTANTIALLY HORIZONTAL IMMOVABLE SURFACE DURING A PORTION OF ITS TRAVEL THROUGH THE BATH, AND DIRECTING VIBRATIONAL ENERGY AT A FREQUENCY OF 200 TO 100 CYCLES PER SECOND UPWARD TOWARD SAID SURFACE AND THE FABRIC SUPPORTED THEREON, THE FABRIC BEING CONDUCTED ACROSS THE SURFACE AT A RATE WHICH WILL PROVIDE TIME FOR THE FABRIC TO BECOME DIMENSIONALLY STABLE TO LAUNDERING. 